i2c: tegra: write clean data to TX FIFO

The Tegra I2C controller's TX FIFO contains 32-bit words. If the final
FIFO entry of a transaction contains fewer than 4 bytes, the driver
currently fills the unused FIFO bytes with uninitialized data. This can
be confusing when reading back the FIFO content for debugging purposes.

Solve this by explicitly initializing the variable containing FIFO data
before filling it (partially) with data. With this change,
send_recv_packets()'s loop's if (is_write) code mirrors the else (i.e.
read) branch.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Reviewed-by: Yen Lin <yelin@nvidia.com>

diff --git a/drivers/i2c/tegra_i2c.c b/drivers/i2c/tegra_i2c.c
index 97f0ca44c59a48cedde0ded34e53eb8579c3647e..a62f30e66ce19e5ec79595c663c5fcd664f472ad 100644 (file)
--- a/drivers/i2c/tegra_i2c.c
+++ b/drivers/i2c/tegra_i2c.c
@@ -224,14 +224,16 @@ static int send_recv_packets(struct i2c_bus *i2c_bus,
 
                if (is_write) {
                        /* deal with word alignment */
-                       if ((unsigned)dptr & 3) {
+                       if ((words == 1) && last_bytes) {
+                               local = 0;
+                               memcpy(&local, dptr, last_bytes);
+                       } else if ((unsigned)dptr & 3) {
                                memcpy(&local, dptr, sizeof(u32));
-                               writel(local, &control->tx_fifo);
-                               debug("pkt data sent (0x%x)\n", local);
                        } else {
-                               writel(*wptr, &control->tx_fifo);
-                               debug("pkt data sent (0x%x)\n", *wptr);
+                               local = *wptr;
                        }
+                       writel(local, &control->tx_fifo);
+                       debug("pkt data sent (0x%x)\n", local);
                        if (!wait_for_tx_fifo_empty(control)) {
                                error = -1;
                                goto exit;